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Determinants — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMathsDeterminants1 Mark
MCQ
Value of $k$, for which $A=\left[\begin{array}{cc}k & 8 \\ 4 & 2 k\end{array}\right]$ is a singular matrix is
  • A
    4
  • B
    -4
  • C
    $\pm 4$
  • D
    $0$
✓

Answer

$\because$ A is a singular matrix.
$
\begin{array}{l}
\therefore|A|=0 \\
\Rightarrow\left|\begin{array}{cc}
k & 8 \\
4 & 2 k
\end{array}\right|=0 \Rightarrow 2 k^2-32=0 \Rightarrow k^2=16 \Rightarrow k= \pm 4
\end{array}$

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